Manganese dioxide for alkaline cells

ABSTRACT

Particulate MnO 2 , having simultaneously a micropore surface area greater than 8.0 m 2 /g, desirably between about 8.0 and 13 m 2 /g and BET surface area of between about 20 and 31 m 2 /g within the context of an MnO 2  having a total intraparticle porosity of between about 0.035 cm 3 /g and 0.06 cm 3 /g produces enhanced performance when employed as cathode active material in an electrochemical cell, particularly an alkaline cell. The average pore radius of the meso and macro pores within the MnO 2  (meso-macro pore radius) is desirably greater than 32 Angstrom.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation in part of application Ser.No. 10/094,199 filed Mar. 8, 2002.

FIELD OF THE INVENTION

[0002] The invention relates to an improved more active form ofmanganese dioxide for use as a cathode active material inelectrochemical cells, particularly alkaline cells.

BACKGROUND

[0003] Manganese dioxide is commonly employed as a cathode activematerial in commercial batteries including heavy duty, alkaline andlithium cells. Battery grade manganese dioxide has been derived fromnaturally occurring manganese dioxide (NMD) and synthetically producedmanganese dioxide. Synthetic manganese dioxide is basically divided intotwo categories: electrolytic manganese dioxide (EMD) and chemicalmanganese dioxide (CMD). NMD because of its high impurity content cannotbe employed in alkaline or lithium cells.

[0004] EMD (electrolytic manganese dioxide) has become the preferredform of manganese dioxide for use in Zinc/MnO₂ alkaline or lithiumcells. EMD (electrolytic manganese dioxide) can be manufactured from thedirect electrolysis of an aqueous bath of manganese sulfate and sulfuricacid. The EMD is a high purity, high density, gamma manganese dioxide,desirable as a cathode material for electrochemical cells particularlyZn/MnO₂ alkaline cells, Zn-carbon and lithium/MnO₂ cells. During theelectrolysis process the gamma EMD is deposited directly on the anodeimmersed in the electrolysis bath. The anode is typically made oftitanium, lead, lead alloy, or graphite. The EMD is removed from theanode, crushed, ground, washed in water, neutralized by washing withdilute NaOH, Na₂CO₃, NH₄OH or LIOH, and dried in a rotary dryer. The EMDproduct can then be used as cathode active material in an alkaline cell,typically a zinc/MnO₂ alkaline cell. The EMD product is generally heattreated to remove residual water before it can be used in a lithiumcell. Conventional electrolysis processes for the manufacture of EMD anda description of its properties appear in Batteries, edited by Karl V.Kordesch, Marcel Dekker, Inc. New York, Vol. 1 (1974), p. 433-488.Conventional electrolysis processes for production of MnO₂ are normallycarried out at temperature between about 80 and 98° C.

[0005] M. Mauthoor, A. W. Bryson, and F. K. Crudwell, Progress inBatteries & Battery Materials, Vol. 16 (1997), pp. 105-110 discloses anelectrolysis method for manufacture of manganese dioxide (EMD). Theelectrolysis is performed at temperatures between 90 and 108° C.Although Mauthoor reports that discharge capacities of MnO₂ synthesizedby electrolysis of an aqueous bath of MnSO₄ and H₂SO₄ at between 95° C.to 108° C. was about 9% higher than that for MnO₂ material produced at95° C., there was no substantial difference among the three MnO₂products produced at electrolysis temperatures of 100° C., 105° C., and108° C. In fact, as Mauthoor increased the electrolysis temperature from105 to 108° C., the percent MnO₂ in the electrolysis product and thedischarge capacity of the MnO₂ product both decreased slightly. Thus,electrolysis at temperatures higher than 108° C. were not attempted orcontemplated.

[0006] M. Ghaemi, Z. Biglari, and L. Binder, Journal of Power Sources,Vol. 102 (2001), pp. 29-34 discloses effects of varying temperature ofthe electrolysis bath during manufacture of the manganese dioxide (EMD).Specifically the properties of the EMD product were investigated whenthe EMD was employed in a rechargeable alkaline cell. The electrolysisbath temperatures were varied in a range between 60° C. and 120° C. Thedata is oriented towards the performance of the rechargeable cell withno data specifically dealing with performance of the EMD in a primarycell. Also, when the rechargeabe cells were tested the first cycleperformance data did not show any improvement with cathodes of EMDproduced under the higher electrolysis bath temperatures, e.g. 115-120°C. compared to conventional bath temperatures, e.g. 80-98° C.

[0007] In commercial EMD production, the electrolysis is normallycarried out at temperatures between 94° C. and 97° C. and at currentdensities between 2 and 10 Amp/ft², more typically between 4 and 10Amp/ft² of anode surface area. A titanium anode and graphite or coppercathode are typically employed. Increasing current density tends toincrease the MnO₂ specific surface area (SSA). When electrolysis iscarried out at conventional temperatures and current density isincreased beyond the normal bounds, there is a tendency for the specificsurface area (SSA) of the MnO₂ product to increase to a level which isoutside (greater than) the desired range of between 18-45 m²/g. Thus, atconventional temperatures it is very difficult to increase the currentdensity and the deposition rate above a level of between about 10 to 11Amp/ft² (108 to 119 Amp m²) without adversely affecting the quality ofthe product.

[0008] In addition, under conventional conditions of temperature andelectrolyte composition, at current densities greater than 10 Amp/ft²(108 Amp/m²) there is a tendency for passivation of the titanium anodeto occur after a period of time, which may be shorter than the normalplating cycle of 1.5 to 3 weeks. The higher the current density, e.g. 12Amp/ft² (130 Amp/m²) rather than 10 Amp/ft² (108 Amp/m²), the soonersuch passivation is likely to occur. Passivation involves the formationof an insulating oxide film on the surface of the titanium, resulting inan increase in the operating Voltage of the anode. Once started theproblem is self accelerating and soon results in a precipitous Voltagerise which exceeds the capability of the power supply followed by a lossof current, ending in complete and irreversible shut-down of the platingprocess. Often a number of anodes will fail simultaneously due topassivation. When this occurs, the anodes must be withdrawn, depositedEMD removed and the anodes must be surface treated to remove thetenacious oxide film prior to being returned to service. This is ahighly disruptive and expensive problem. In a commercial setting, greatcare is taken to avoid anode passivation and a margin of safety ispreserved in setting the current density below that which borders onpassivation, EMD quality considerations aside.

[0009] V. K. Nartey, L. Binder, and A. Huber, Journal of Power Sources,Vol. 87 (2000), p. 205-211 describes an electrolysis process for makingMnO₂ wherein the electrolysis bath was doped with TiOSO₄. The MnO₂ wasused in an alkaline rechargeable battery. The reference states at page210, col. 1 that the MnO₂ with TiOSO₄ doping (called M₂, Table 7)performed poorly on the initial discharge cycle (i.e. similar to aprimary, non-rechargeable cell) despite a high specific surface area.When the bath was doped with TiO₂ the MnO₂ product (called M₁, Table 7)performed better on the initial discharge cycle, but still did notperform as well as the control MnO₂ (commercial grade EMD Tosoh GH-S).The electrolysis bath for the experiments described in Huber, et al. wasmaintained at conventional temperature of 98° C. and was performed atconventional current density of 6 milliAmp/cm² (5.57 Amp/ft²) based onanode surface area.

[0010] Conventional battery grade manganese dioxide does not have a truestoichiometric formula MnO₂, but is better represented by the formulaMnO_(X), wherein x is typically between about 1.92 to 1.96,corresponding to a manganese valence of between about 3.84 and 3.92.Conventional EMD may typically have a value for x of about 1.95 or 1.96,corresponding to a manganese valence of 3.90 and 3.92, respectively. Inaddition to manganese (Mn) and oxygen (O), conventional electrolyticmanganese dioxide (EMD) also contains a certain quantity of SO₄ ⁼ ionsand of H⁺ ions (protons) in the crystal lattice. When heated totemperatures above 110 deg. C, the lattice protons combine with oxygenand are liberated as H₂O. Conventional EMD also has a real density ofbetween about 4.4 and 4.6 g/cm³.

[0011] CMD has for many years been economically produced commercially,but such commercial chemical processes while yielding high purity MnO₂,do not yield densities of MnO₂ comparable to that of EMD. As a resultEMD has become the most widely used form of battery grade MnO₂,particularly for alkaline and lithium cells, since in such applicationit has become most desirable to employ high density MnO₂ to increase thecapacity of these cells. However, in the course of conventionalmanufacture of EMD, it has been difficult to significantly alterimportant properties, such as surface area and activity, withoutadversely affecting the density.

[0012] U.S. Pat. No. 2,956,860 (Welsh) discloses a chemical process forthe manufacture of battery grade MnO₂ by employing the reaction mixtureof MnSO₄ and an alkali metal chlorate, preferably NaClO₃. This processis known in the art as the “Sedema process” for manufacture of chemicalmanganese dioxide (CMD). The reaction is carried out in the presence ofsolid MnO₂ particles which act as a catalyst and nucleation site fordeposition of the MnO₂ formed from the reaction of MnSO₄ and alkalimetal chlorate. As the reaction proceeds, MnO₂ which is formedprecipitates onto, and even into, the MnO₂ substrate particles. Theresulting MnO₂ product from the Sedema process takes the form ofsmooth-surfaced spherical particles. However, the MnO₂ does not have adensity as high as that obtained in EMD. Significantly higher densitiesof the MnO₂ product are not obtainable by controlling reaction rate withalkali metal chlorate. Also the MnO₂ produced from the process disclosedin this reference cannot be readily deposited on substrates other thanmanganese oxides. If an alternative substrate or no substrate isemployed, the MnO₂ product precipitates out during formation as a lightfluffy product which is unacceptable as battery grade MnO₂.

[0013] An article by K. Yamamura et. al., (“A New Chemical ManganeseDioxide for Dry Batteries,” Progress in Batteries & Battery Materials,Vol. 10 (1991), p. 56-75) discloses another process for manufacturinggamma MnO₂. The process referenced as the “CELLMAX” (CMD-U) processinvolves special treatment of purified crystalline MnSO₄ to produce anelectrochemically active high density gamma MnO₂. The product has asurface area and particle appearance similar to electrolytic manganesedioxide (EMD), but differs in its pore size, tap density and particlesize distribution. The process consists of the steps of leachingmanganese ore, crystallizing, adjusting the pH, compressing andgrinding. In the process the manganese sulfate solution extracted fromthe manganese ore is purified, crystallized under optimum conditions androasted at very high temperature. The product Mn₃O₄ is oxidized to Mn₂O₃by oxygen at high temperature. The Mn₂O₃ is subjected to acid treatmentto yield gamma MnO₂ which in turn is compressed to yield a higherdensity. Although a high density gamma MnO₂ product is reported, theprocess has the disadvantage of involving a number of reaction andprocessing steps which require careful control and would be expensive toimplement.

[0014] There are increasing commercial demands to make primary alkalinecells better suited for high power application. Modern electronicdevices such as cellular phones, digital cameras, toys, flash units,remote control toys, camcorders and high intensity lamps are examples ofsuch high power applications. Such devices demand high power, forexample, an AA cell may be required to deliver high power between about0.5 and 2 Watt which corresponds to current drain rates between about0.5 and 2 Amp, more usually between about 0.5 and 1.5 Amp. Thus, it isdesirable to provide a way of reliably increasing the useful servicelife of conventional primary alkaline cells particularly for cells to beused in high power applications, without adversely affecting cellperformance on medium or low power applications.

[0015] Accordingly it is desirable to produce an improved form ofmanganese dioxide which extends the useful service life ofelectrochemical cells, particularly alkaline cells intended for a rangeof normal service including high power applications.

Definitions

[0016] A manganese dioxide particle can be visualized as formed ofagglomerates of MnO₂ crystallites. In the case of EMD the crystallitesare gamma phase MnO₂ crystals. (Gamma phase MnO₂ crystal is believed toresult from the intergrowth of two phases pyrolusite and ramsdellite.)The crystallites are distinct microstructures which agglomerate intoMnO₂ particles. The crystallites are typically between about 50 and 200Angstrom long. There is thus void volume (porosity) between thecrystallites within each particle (intraparticle porosity) and betweenthe MnO₂ particles themselves (interparticle porosity) The averageparticle size of the MnO₂ particles can be readily controlled bygrinding. Battery grade MnO₂ is typically ground to a mean averageparticle size of between about 1 and 100 micron, desirably between about10 and 50 micron, typically about 35 micron. It should be noted that thetotal surface area (BET surface, m²/g) of conventional MnO₂ particles istypically over 99 percent internal. Therefore, grinding to differentparticle sizes normally has little effect on the BET surface, m²/g.

[0017] The solid MnO₂ material is thus defined by the crystallites. EachMnO₂ particle occupies an overall volume which is defined by the outerboundary of the MnO₂ particle. The overall volume of a single MnO₂particle is comprised of the volume of the MnO₂ crystallites within theparticle and the intra particle porosity, that is, the volume of thepores between the individual crystallites. Each one of the crystallitesis known to have very fine crystallographic tunnels therein (2-4Angstrom width) which are considered as part of the crystallinestructure and not part of the intra particle porosity. In addition thereis pore volume between the MnO₂ particles. This is referred to asinterparticle porosity.

[0018] The bulk density (apparent density) of an MnO₂ powder sample isdefined as the weight of the sample divided by it total apparent volume.The apparent volume comprises the volume of crsytallites and volume ofpores which includes the interparticle pores as well as theintraparticle pores. The tapped bulk (apparent) density is themeasurement of apparent density wherein the MnO₂ powder is first placedin a graduated cylinder and tapped down a defined number of times. EMDpowder for use as cathode active material typically has a tapped bulkeddensity between about 2.2 and 2.6 gm/cm³.

[0019] The intraparticle pores, that is, the pores within an individualMnO₂ particle, can be classified into three regimes, namely, micropores,mesopores and macropores. These latter terms are used herein shall beassumed to be open pores within each particle, that is, having somepathway accessible by nitrogen gas from within the pore out to theenvironment external to the particle. There can be a certain smallpercentage of void volume trapped as closed pores within each MnO₂particle. Such closed pores cannot be measured by conventional methodsand are generally assumed as part of the real volume of Mnb₂ matter.Thus the term real volume of an MnO₂ sample or particle is the volume ofthe MnO₂ crystallites including the closed pores. The intraparticlepores (micro and meso-macro pores) or total intraprticle porosity asreferenced herein shall be understood to refer to open pores within theMnO₂ particle reachable by nitrogen gas used in the various testingmethods described herein, e.g BET (Brunauer, Emmett, Teller), BJH(Barrett, Joyner, Halenda), and deBoer “t” methods.

[0020] The total intraparticle porosity, cm³/g, as reported herein andas conventionally reported in the literature is defined as the totalintraparticle pores (micropores, mesopores and macropores within theMnO₂ particles) divided by the weight of the MnO₂ sample.

[0021] The micropores as referenced herein are defined as intraparticlepores having a diameter of less than or equal to 20 Angstrom. Mesoporesas referenced herein are defined as intraparticle pores having adiameter of between about 20 and 500 Angstrom. The macropores asreferenced herein are defined as intraparticle pores having a diameterof above about 500 Angstrom. The term meso-macro pores as used hereinand in the claims shall mean intraparticle pores which make up the totalof mesopores and macropores in the MnO₂, wherein the pore diameter ofthe meso and macro pores (meso-macro pores) are greater than that of themicropores. Namely, the meso-macropores as defined herein areintraparticle pores having a diameter greater than 20 Angstrom and themicropores are intraparticle pores having a diameter less than or equalto 20 Angstrom. The micropore surface area and micropore volume can bemeasured from the deBoer “t” method as described, for example, in thebook, “Adsorption by Powders and Porous Solids”, F. Rouquerol, J.Rouquerol & K. Sing, Academic Press, 1999, ISBN 0-12-598920-2, pgs.174-176 and 222-224 and in the “Quantachrome Manual for the AutosorbMultistation Gas Sorption System”, Quantachrome Corp., Boynton Beach,Fla., pgs. II-13 to II-16. The total intra particle pore volume (micro,meso and macropores within the particles) can be measured by theBarrett, Joyner, Halenda desorption method (BJH desorption method. Thismethod is described, for example, in the preceding reference, pgs. 199and 444 and in the Quantachrome Manual for the Autosorb Multistation GasSorption System, Quantachrome Corp., Boynton Beach, Fla., pgs. II-10 toII-12. The BET surface area for the MnO₂ particles, m²/g, can beobtained from the well known BET (Brunauer, Emmett and Teller) methodcarried out in accordance with ASTM Standard Test Method D4820-99.

[0022] The term BET surface area (m²/g) as used herein shall mean thestandard measurement of particulate surface area by gas (nitrogen and/orother gasses) porosimetry as is recognized in the art. The BET surfacearea measures the total surface area on the exterior surface of the MnO₂particle and also that portion of surface area defined by the open poreswithin the particle available for gas adsorption and desorption whenapplied. BET surface area determinations as reported herein are carriedout in accordance with ASTM Standard Test Method D4820-99. The MnO₂powder can be outgassed under vacuum typically at a temperature of 150°C. for 7 hours, under vacuum, in an instrument such as QuantachromeDegasser manufactured by Quantachrome Co. The BET surface area can bedetermined from nitrogen gas adsorbate and use of a multi-point BETequation to calculate the BET surface using the software provided by theinstrument manufacturer.

[0023] The true crystalline density of MnO₂, that is the density of atrue EMD or CMD crystallites is about 4.9 g/cm³. The term real density(or skeletal density) of an MnO₂ powder sample is the weight of thesample divided by the real volume (volume of the MnO₂ crystallites plusclosed pores). The real density of CMD is typically between about 4.6and 4.7 g/cm3. The real density of EMD is typically between about 4.4and 4.6 g/cm3. The particle density of CMD is typically about 3.0 g/cm3and the particle density of EMD as used in electrochemical cells istypically about 3.3 g/cm3. The average particle density is the weight ofthe sample divided by the particle real volume, that is, the volume ofcrystallites and total intraparticle pores (micro, meso and macropores)within the particles. That is, the particle density does not include theinterparticle porosity (volume of pores between the particles).

[0024] Particulate EMD is presently commercially available with BETsurface area of between 20 and 40 m²/g and micropore area between 0 and7.3 m²/g. The literature does not report EMD which simultaneously hasgreater than 8.0 m²/g of micropore area along with a BET surface area ofless than 31 m²/g, e.g. 20 to 31 m²/g. This is irrespective of the totalintra particle porosity (total pore volume per gram within the MnO₂particle.) EMD typically has an intraparticle total pore volume ofbetween 0.04 and 0.06 cm³/g.

SUMMARY OF THE INVENTION

[0025] In a principal aspect of the invention it has been determinedthat particulate MnO₂, having simultaneously a micropore surface areagreater than 8.0 m²/g, desirably between about 8.0 and 13 m²/g and BETsurface area of between about 20 and 31 m²/g within the context of anMnO₂ having a total intraparticle porosity of between about 0.035 cm³/gand 0.06 cm³/g, desirably between about 0.035 cm³/g and 0.05 cm³/g, willproduce enhanced performance when employed as cathode active material inan electrochemical cell, particularly an alkaline cell. It has beendetermined when the MnO₂ has the above parameters simultaneously, theaverage radius of the meso-macropores within the MnO₂ particles will bedesirably large, namely, greater than 32 Angstrom, from calculationsbased on cylindrical pore geometry. The term “average” as used hereinunless otherwise defined shall be taken to be the arithmetic meanaverage. This is believed to facilitate excellent ionic conduction ofwater and electrolyte hydroxyl (OH—) ions. The higher meso-macroporeaverage radius together with the high micropore surface area helps toachieve the excellent performance of the MnO₂ of the invention ascathode active material in alkaline cells.

[0026] In a specific aspect the manganese dioxide simultaneously has aBET surface area between about 20 and 28 m²/g and a micropore areabetween 8 and 13 m²/g, and an average meso-macropore radius greater thanabout 32 Angstrom, with the total porosity, based on pores within themanganese dioxide, being between about 0.035 cm³/g and 0.040 cm³/g.

[0027] In another specific aspect the manganese dioxide simultaneouslyhas a BET surface area between about 20 and 30 m²/g and a micropore areabetween 8 and 13 m²/g, and an average meso-macropore radius greater thanabout 32 Angstrom, with the total porosity, based on pores within themanganese dioxide, being between about 0.040 cm³/g and 0.045 cm³/g.

[0028] In another specific aspect the manganese dioxide simultaneouslyhas BET surface area between about 20 and 31 m²/g and a micropore areabetween 8 and 13 m²/g, and an average meso-macropore radius greater thanabout 32 Angstrom, with the total porosity, based on pores within themanganese dioxide, being between about 0.045 cm³/g and 0.050 cm³/g.

[0029] The excellent battery performance utilizing MnO₂ cathode activematerial having simultaneously a micropore area greater than 8.0 m²/g,desirably between about 8.0 and 13 m²/g and BET surface area of betweenabout 20 and 31 m²/g may possibly be explained as follows with respectto an alkaline cell: The micropores (micropore surface area greater than8.0 m²/g) within the individual MnO₂ particles are responsible for orgreatly facilitate attainment of high voltage, high rate and highcapacity cell performance. This is due to the presence of a high levelof surface water and bound protons (H⁺ions) within the micropores. Themesopores and macropores within the individual MnO₂ particles aretheorized to be responsible for conduction of water and hydroxyl (OH—)ions into and out of the MnO₂ particles and also for the conduction ofthese species across the total cathode thickness. (Typical cathodethickness in an AA cell is approximately 2.2 mm.) It is theorized thatthe average radius of the meso-macropores should be sufficiently large,desirably greater than 32 Angstrom, to enable the highest rate diffusionand electro-migration of water and hydroxyl (OH—) through the cathodewhich in turn maintains a high rate of electrochemical reaction.

[0030] The MnO₂ of the invention can be made in the form of EMD(electrochemical manganese dioxide). It will be appreciated that oncethe BET surface area (BET method) and micropore surface area (measuredby deBoer “t” method) and total intraparticle pore volume (measured byBJH desorption method) are determined, the average meso-macro poreradius can be estimated. The average meso-macro pore radius can becalculated assuming a model of cylindrical shaped pores. (A samplecalculation for the average radius of the meso-macro pores is presentedin the examples herein.)

[0031] Excellent discharge performance is achieved when the MnO₂ of theinvention is utilized as cathode active material in electrochemicalcells, particularly zinc/MnO₂ alkaline cells under normal operatingconditions. Enhanced performance can be achieved when the MnO₂ (EMD) ofthe invention as used in zinc/MnO₂ alkaline cells particularly underhigh power application, e.g. at current drains between about 0.5 and 1.5Amp or power output of between about 0.5 and 1.5 Watt for a AA alkalinecell. For example, when the MnO₂ of the invention is utilized as cathodeactive material in a zinc/MnO₂ AA alkaline cell an excellent capacity ofabout 500 to 680 milliAmp-hours can be achieved at continuous 1 Ampcurrent drain to a cut off voltage of 1.1 volt. When the EMD of theinvention is utilized as cathode active material in a zinc/MnO₂ AAalkaline cell an excellent capacity of about 1200 to 1500 milliAmp-hourscan be achieved at continuous 1 Amp current drain to a cut off voltageof 0.9 volt.

BRIEF DESCRIPTION OF THE FIGURES

[0032]FIG. 1 is a plot of allowed BET total surface area and microporesurface area for particulate MnO₂ at total porosity of 0.035 cm³/g.

[0033]FIG. 2 is a plot of allowed BET total surface area and microporesurface area for particulate MnO₂ at total porosity of 0.040 cm³/g.

[0034]FIG. 3 is a plot of allowed BET total surface area and microporesurface area for particulate MnO₂ at total porosity of 0.045 cm³/g.

[0035]FIG. 4 is a plot of allowed BET total surface area and microporesurface area for particulate MnO₂ at total porosity of 0.050 cm³/g.

DETAILED DESCRIPTION EXAMPLE 1

[0036] The following example illustrates a method of calculating theaverage meso-macro pore radius, R, within a sample of particulatemanganese dioxide. It will be understood that all of the parametersreferenced herein are with respect to properties within the manganesedioxide particles, that is, intra particle properties. There is noconcern herein with interparticle properties, for example, void volumesbetween the particles (interparticle porosity).

[0037] It has been determined desirable to obtain particulate manganesedioxide, preferably, particulate electrolytic manganese dioxide (EMD)which has an average meso-macro pore radius greater than 32 Angstrom(32×10⁻10 meter) in conjunction with particulate manganese dioxidehaving a total intra particle porosity of between about 0.035 and 0.06cm³/g. This is irrespective of the average particle size.

[0038] Since the average radius of the meso-macro pores within a sampleof MnO₂ particles cannot be measured directly, a method is presentedwherein the average meso-macro radius can be calculated from obtainablesurface area, and pore volume measurements. Specifically in a givensample of particulate MnO₂, the meso-macro pore average radius can becalculated once the BET total surface area, cm²/g; total intraparticlepore volume, cm³/g; micropore surface area, cm²/g; and micropore volume,cm³/g are determined. The total surface area, cm²/g can be determined byconventional BET (Brauner, Emmett, and Teller) methods as referencedherein. The total intraparticle pore volume, cm³/g, can be determinedfrom the BJH (Barrett, Joyner, and Halenda) cumulative desorption volumemethod. The micropore surface area, cm²/g, can be determined from thedeBoer “t” micropore area determination method. The micropore volume,cm³/g, can be determined from the deBoer “t” micropore volumedetermination method.

[0039] The average meso-macro pore radius can then be calculated asfollows:

[0040] Assume that all pores are in the shape of cylinders. This is aconventional simplifying assumption employed in calculations of thistype. The average pore radius is therefore that radius which would givea total calculated pore volume of the meso-macro pores in agreement withexperiment, if all the pores were cylinders having identical diameters.

[0041] Then, meso-macro pore area=n(2πRL)

[0042] Where:

[0043] n is the number of meso-macro pore cylinders in 1 gram ofparticulate MnO₂ sample;

[0044] R is the average radius of the meso-macro pore cylinders;

[0045] L is the average length of the meso-macro pore cylinders.

[0046] Assume a basis of 1 gram of MnO₂ sample.

[0047] Then:

Meso-macropore volume=total pore volume−micropore volume=n(πR ² L)

Meso-macropore area=BET total surface area−micropore surfacearea=n(2πRL)

[0048] Dividing the two preceding equations:

Meso-macropore volume/meso-macropore area ═R/2

[0049] Therefore,

R=2×Meso-macropore volume/meso-macropore area$R = {2 \times \frac{\left\lbrack {{{Total}\quad {pore}\quad {volume}} - {{micropore}\quad {volume}}} \right\rbrack}{\left\lbrack {{{Total}\quad {surface}\quad {area}} - {{micropore}\quad {surface}\quad {area}}} \right\rbrack}}$

[0050] Thus, the average meso-macropore radius, R (expressed in cm), iscalculable once the total pore volume, cm³/g; micropore volume, cm³/g;BET total surface area, cm²/g; and micropore surface area, cm²/g aredetermined. These four parameters are measurable by the above referencedBET (Brauner, Emmett, and Teller), BJH (Barrett, Joyner, and Halenda)and deBoer “t” methods as above discussed. (Note: 1 cm=108 Angstroms)

DISCUSSION OF THE FIGURES

[0051]FIG. 1 shows the range of micropore area and BET total surfacearea required simultaneously for particulate MnO₂ samples in order toobtain the desired average meso-macro pore radius greater than 32Angstrom at total intraparticle porosity for the sample at 0.035 cm³/g.The average meso-macro pore radius was calculated by the method setforth in Example 1. Implicit in this is a micropore volume cm³/g,measured or calculated by the de Boer “t” method for nitrogenabsorption/desorption. (As shown in Example 1 the micropore volume isone of the parameters needed, along with the total intraparticle porevolume, BET total surface area, and micropore area in order to calculatean average meso-macro pore radius.)

[0052] It will be seen that from the deBoer treatment of nitrogensorption data, measured micropore volumes (cm³/g) for all MnO₂ materialstested fall in the range of 0.0000 to 0.0052 cm³/g., In all cases thisis less than 16% (generally less than 10%) of the measured intraporevolumes for the same collection of MnO₂ materials (intrapore volumesrange from 0.034 to 0.200 cm³/g). Comparing measured micropore volumes(cm³/g) to measured micropore areas (m²/g), it is possible to expressthe micropore volume by the relation: micropore volume (cm³/g)=microporearea (m²/g)×K, where K ranges from 0.000433 to 0.000507, for all MnO₂materials as represented in Table 1. This may be expressed approximatelyas: micropore volume (cm³/g)=micropore area (m²/g)×0.00047. Since themicropore volume is generally about one magnitude smaller than theintraparticle volume (sometimes 2 orders smaller), this is sufficientlyaccurate to allow us to calculate the meso-macropore volume according tothe relation:

meso-macropore volume=intra particle volume−microporevolume=intraparticle volume−0.00047×micropore area.

[0053] Using this approximation, the maximum error in the calculatedmeso-macropore volume would be 0.00038 cm³/g in the case of EXP1,compared to a meso-macropore volume of 0.037 cm³/g, i.e. about 1%. Theerror in the calculated meso-macropore radius, which is proportional to(volume) 1/² (cylindrical pore model), would then be less than 0.5%.

[0054] Thus, when calculating meso-macropore volume and radius, and whenconstructing graphs which depend on the meso-macropore radius, it isreasonable to approximate the micropore volume as a function of themicropore area according to the relation given above.

[0055]FIG. 1 shows that at total intraparticle porosity of 0.035 cm³/g,the micropore area should be in a range between about 8.0 and 13 m²/gsimultaneously with a BET total surface area of between about 20 and 28m²/g. The BET total surface is presented in logarithmic scale. Theunfilled circles shown in FIG. 1 all have an average meso-macroporeradius greater than 32 Angstrom. The largest unfilled circles shown inFIG. 1 have an average meso-macro pores radius much larger than 32Angstrom. The circles are drawn to scale with the size circlerepresenting a 32 Angstrom radius is shown in the lower left hand cornerof the figure.

[0056]FIG. 2 shows the range of micropore area and BET total surfacearea required simultaneously for particulate MnO₂ samples in order toobtain a desired average meso-macro pore radius greater than 32 Angstromat total intraparticle porosity for the sample at 0.040 cm³/g. Theaverage meso-macro pore radius was calculated by the method set forth inExample 1.

[0057]FIG. 2 shows that at total intraparticle porosity of 0.040 cm³/g,the micropore area should be in a range between about 8.0 and 13 m²/gsimultaneously with a BET total surface area of between about 20 and 31m²/g. (The unfilled circles shown in FIG. 2 all have an averagemeso-macropore radius greater than 32 Angstrom.)

[0058]FIG. 3 shows the range of micropore area and BET total surfacearea required simultaneously for particulate MnO₂ samples in order toobtain a desired average meso-macro pore radius greater than 32 Angstromat total intraparticle porosity for the sample at 0.045 cm³/g. Theaverage meso-macro pore radius was calculated by the method set forth inExample 1.

[0059]FIG. 3 shows that at total intraparticle porosity of 0.045 cm³/g,the micropore area should be in a range between about 8.0 and 13 m²/gsimultaneously with a BET total surface area of between about 20 and 31m²/g. (The unfilled circles shown in FIG. 3 all have an averagemeso-macropore radius greater than 32 Angstrom.)

[0060]FIG. 4 shows the range of micropore area and BET total surfacearea required simultaneously for particulate MnO₂ samples in order toobtain a desired average meso-macro pore radius greater than 32 Angstromat total intraparticle porosity for the sample at 0.050 cm³/g. Theaverage meso-macro pore radius was calculated by the method set forth inExample 1.

[0061]FIG. 4 shows that at total intraparticle porosity of 0.050 cm³/g,the micropore area should be in a range between about 8.0 and 13 m²/gsimultaneously with a BET total surface area of between about 20 and 31m²/g. (The unfilled circles shown in FIG. 4 all have an averagemeso-macropore radius greater than 32 Angstrom.)

[0062] In FIGS. 2 and 3, a number of commercial EMD materials andexperimental samples (EXP samples, according to this invention) areshown. Values of BET area, micropore area, intraparticle pore volume,micropore volume, and calculated meso-macropore radius for thesematerials are given in Table 1. TABLE 1 Properties of Applicant'sExperimental vs. Existing Commerical Battery Grade Manganese Dioxide¹Intra- Micropore Micropore particle Meso-macro IC # or BET Area AreaVolume Volume Pore Radius Other ID Sample Name (m2/g) (m2/g) (cc/g)(cc/g) (Angstrom) EXP1 EMD EXP1 26.74 10.31 0.00523 0.03716 38.87 EXP2EMD EXP2 27.73 8.27 0.00361 0.038 35.34 A EMD KM Trona D 31.98 7.250.00367 0.0413 30.43 B EMD KM HP 23.31 7.22 0.00366 0.0343 38.09 C EMDTosoh GHPT 25.64 0 0.00000 0.0423 33.00 D EMD Tosoh HHP 40.87 8.830.00436 0.0516 29.49 E EMD Chemetals 37.09 8.69 0.00428 0.0438 27.83 FEMD Mitsui 30.37 4.063 0.00186 0.04528 33.01 10 EMD KM Trona D 632148.87 8 0.00370 0.0791 36.90 8 CMD Far M 92.46 0 0.00000 0.2023 43.76 22CMD Japan 3/84 51.7 0 0.00000 0.1816 70.25 G EMD Delta TL C878/I42 57.0810.52 0.00499 0.0699 27.88 21 EMD 40.41 4.71 0.00227 0.1127 61.87 H EMDKM Low Na 9864 45.55 9.58 0.00461 0.0567 28.96 12 CMD Synth MnO2 MHV95.35 0 0.00000 0.1764 37.00 I EMD KM TronaD Feb 02 26.98 5.456 0.002450.03876 33.74 J XiangtanA Feb 02 34.94 6.026 0.00261 0.04988 32.70 KXiangtanB Feb 02 43.92 11.54 0.00520 0.04877 26.91 Avg → 0.0750 Median →0.0499

[0063] All of the commercial samples fall outside the range of BET areaand micropore area claimed in this invention, that is none of thecommercial materials possess simultaneously a BET area of 20-31 m2/g anda micropore area greater than 8.0 m2/g. Although the commercialmaterials exhibit a wide range of pore volumes from 0.034 cm3/g to 0.200cm3/g, it doesn't matter on which plot they are displayed as thisdoesn't alter the BET or micropore values. For the sake of conveniencewe have shown these on the plots for intraparticle pore volumes of 0.040and 0.045 cm3/g. The picture is unchanged for all other intraparticlepore volumes greater than 0.045 cm3/g since only open circles appearbeyond this point in the field bounded by BET area from 20 to 31 m2/gand micropore area from 8.0 to 13.0 m2/g. The experimental samples ofthis invention EXP1 and EXP2 fall well within the range of this field,i.e. BET area of 20 to 31 m2/g and, simultaneously, micropore areagreater than 8.0 m2/g: BET Area (m2/g) Micropore Area (m2/g) EXP1 26.710.36 EXP2 28.2 8.70

[0064] Even the acknowledged leading commercial EMD material for highpower performance, Sample B=KMHP (Kerr McGee High Power EMD) fallsoutside of the region claimed; it has a micropore area less than 8.0m2/g. KMHP 23.3 7.2

[0065] It might seem a simple matter to increase the micropore area ofthis sample somewhat, in order to move this material into the desiredrange. But the situation is quite the contrary. It is extremelydifficult to find conditions for electrolytic deposition of EMD whichcan unilaterally adjust any one parameter, such as micropore area,without also affecting other key parameters such as BET area and totalintraparticle porosity.

[0066] Thus, one could try to increase the current density in order togain micropore area. But a well known consequence of increasing currentdensity is to rapidly increase BET area. As BET area increases thecalculated average meso-macropore radius will decrease until it fallsbelow the limit of 32 Angstroms, required for good ionic and watertransport in the MnO₂ particle.

[0067] This is especially true for an MnO₂ material having a lowintraparticle volume such as KMHP EMD (sample B), i.e. intraparticlevolume=0.00366 cc/g. In this case from FIG. 1 we see that for amicropore area around 7.2 m2/g the upper limit for BET area is less than28 m2/g. Hence, the KM HP material is already close to the limit, andany attempt to increase micropore area by increasing current densityruns the risk of exceeding the desired BET limit.

[0068] We have found that a preferred condition for depositing EMDhaving BET area of 20-31 m2/g and simultaneously having micropore areagreater than 8.0 m2/g, along with a reasonable intraparticle porosity of0.030 to 0.060 cm³/g is to operate the deposition cell attemperatures>110 deg. C and super atmospheric pressure, as described inour earlier patent application, now U.S. Pat. No. 6,585,881 B2. Thiscondition alone (Temperature >110 deg. C) is not sufficient to guaranteeobtaining material within the desired range of BET and micropore areas.In addition to temperature, the current density and electrolytecomposition must be adjusted to their respective optima as well.

[0069] For example, to produce EMD sample EXP2, the following depositionconditions were employed: Temperature 120.3 deg. C. Pressure  29.9 psigMnSO4 concentration  0.75 mole/liter H2SO4 concentration  1.04mole/liter Current density  9.38 A/ft2 Duration of plating   165 hoursAnode Titanium, commercial grade, sandblasted surface Cathodes GraphiteWeight of plated EMD 1,575 grams

[0070] The above conditions are not meant to be exclusive, nor is itclaimed that they are completely optimal; only that they have been foundto produce a material within the desired range of BET and microporeareas.

[0071] At the same nominal temperature of 120 deg. C, the averageconditions in the cell for EXP1 were: Temperature 120.0 deg. C. Pressure 15.0 psig MnSO4 concentration  0.88 mole/liter H2SO4 concentration 0.63 mole/liter Current density  6.19 A/ft2 Duration of plating   257hours Anode Titanium, commercial grade, sandblasted surface CathodesGraphite Weight of plated EMD   284 grams Ti doping in the product 2,160ppm Ti

[0072] It should be noted that while EXP2 was produced on largeelectrodes (83.25 in2) in an electrolyte bath of constant composition(continuously refreshed electrolyte), EXP1 was produced on smallerelectrodes (14.88 in2) in a large volume (11 to 12 liters) of staticelectrolyte, hence with a variation in electrolyte composition of +/−15%compared to the average values quoted above. In this trial (EXP1), wealso allowed the Ti anode to corrode, prior to initiating plating, whichprovided some doping of the bath and the final deposit with Titanium(i.e. 2,160 ppm of Ti in the final EMD powder).

[0073] In both of these trials, those familiar with the practice ofcommercial EMD plating will appreciate that acid levels were generallyhigher than that employed in commercial EMD plating baths. These rarelyexceed 0.5 mole/liter of H2SO₄, for fear of passivating the Ti anodes.No tendency towards passivation was seen during these trials. This isattributed to the very high plating temperature employed, around 120deg. C, which is possible only in a pressurized cell. Ordinarycommercial practice is to plate at temperatures of 94 to 97 deg. C, inan unpressurized cell at 0.3 to 0.5 mole/liter H2SO₄. It is believedthat high acid is one of the conditions (in addition to elevatedtemperature) which favors the production of high quality EMD as definedin this invention, i.e. with BET area in the range 20-31 m2/g and,simultaneously, micropore area greater than 8.0 m2/g.

[0074] The conditions mentioned above are not meant to limit thisinvention. Any temperature above 110 deg. C is believed practical andthe ideal range of temperature is believed to be above 12° C. up to thepoint where construction of pressurized cells becomes economicallyinefficient. For example up to 15° C. and up to 125 psig. Theelectrolysis, for example, can desirably be carried out at elevatedtemperatures between about 110° C. and 180° C., preferably between about115° C. and 155° C., also advantageously between 120° C. and 155° C. andcorresponding superatmospheric vapor-liquid equilibrium pressure, oreven at somewhat higher pressures. The above desired properties ofmanganese dioxide having a BET surface of between about 20 and 31 m²/gand simultaneously a micropore area between about 8.0 and 13 m2/g withinthe context of a total porosity between about 0.035 and 0.06 cm³/g ismore readily achievable at operation of the electrolysis at suchelevated temperatures and superatmospheric pressure.

[0075] The superior performance of samples EXP1 and EXP2 is illustratedin the performance results summarized in Tables 2 and 3. Tables 2 and 3present discharge data for practical AA alkaline zinc cells constructedwith the EXP1 and EXP2 manganese dioxide materials compared tocommercial EMD; either 100% Trona D EMD (Kerr McGee Corporation) or a50/50 blend of Trona D EMD with KMHP EMD (Kerr McGee High Power EMD).TABLE 2 Comparative Performance of EMD of Present Invention versusCommercial EMD Materials at 1 Ampere Continuous Discharge to DifferentEnd Point Voltages Cell EMD A-hrs to A-hrs to A-hrs to A-hrs to BuildType (s) 1.1 V 1.0 V 0.9 V 0.8 V GM 826- 100% 0.509 0.893 1.159 1.306833 Trona D GM 826- EXP1 0.686 1.031 1.322 1.508 833 Present +34.8%+15.5% +14.1% +11.5% invention G42 50/50 0.423 0.699 0.913 1.060 Trona D/ KMHP G42 EXP2 0.521 0.813 1.044 1.211 Present +23.2% +16.3% +14.4%+14.2% invention

[0076] TABLE 3 Comparative Performance of EMD of Present Inventionversus Commercial EMD Materials on the 1 Ampere 10 Second / Minute, 1hour / 12 Hour Simulated Photoflash Test to Different End Point VoltagesCell EMD Pulses to Pulses to Pulses to Pulses to Build Type (s) 1.1 V1.0 V 0.9 V 0.8 V G42 50/50 221 375 570 651 Trona D / KMHP G42 EXP2 232385 581 665 This +5.0% +2.7% +1.9% +2.2% invention

[0077] It is seen from Table 1 that the gains on the 1 Ampere continuousdrain are very substantial. The difference in the absolute performancebetween builds GM 826-833 and G42 are attributed to the use of differentlots of materials and components, different assembly tools and personneland slight differences in the ambient temperature during discharge.(These two builds were made more than 1 year apart.) The comparisonsbetween experimental EXP1 and EXP2 materials and control EMD, within agiven build, show the clear superiority of the former.

[0078] It is seen from Table 2 that small, but significant improvementsare also realized on the simulated photoflash test when EMD is preparedaccording to the teachings of the present invention, i.e. EXP2. Nophotoflash data was available for EXP1 due to a scarcity of cells, basedon the small quantity of EMD produced on the 14.88 in2 electrodes, mostof which was consumed in analyses and in the few cells discharged on the1 Ampere continuous drain.

[0079] Conventional commercial electrolysis processes for preparation ofelectrolytic manganese dioxide (EMD) have generally been carried outunder atmospheric conditions and temperatures below 98° C., moretypically between 94° C. and 97° C. For production of CMD thetemperatures have been somewhat lower, between about 85° C. and 95° C.,carried out at atmospheric pressure. It will be observed from the datapresented in the tables that manganese dioxide produced by suchconventional processes do not have the combination of BET surface areaand micropore area at total porosity between 0.035 cm³/g and 0.06 cm³/gwhich Applicant has determined can result in a manganese dioxide havinga meso-macro pore average radius greater than 32 Angstrom. Specifically,an analysis of the data reported in the accompanying tables reveals thatnone of the prior art conventional battery grade manganese dioxide,whether produced by conventional electrolysis (EMD) or by conventionalchemical processing (CMD), results in a manganese dioxide product havingthe combination of BET surface area between 20 and 31 m²/gsimultaneously with and micropore area between about 8 and 13 m²/g,within the context of a total intraparticle porosity of between about0.035 and 0.06 cm³/g, more typically between about 0.035 and 0.05 cm³/g.

[0080] It is thus believed that the prior art has failed to recognizethat improved alkaline cell performance is attainable from manganesedioxide having the above combination of the BET surface between 20 and31 g/m² and micropore surface between about 8.0 and 13 g/m² within thecontext of a total porosity between about 0.035 and 0.06 cm³/g, moretypically between about 0.035 and 0.05 cm³/g.

[0081] Secondly, the prior art has not focused on changing the operatingconditions of commercial electrolysis to significantly highertemperatures and pressures in order to produce electrolytic manganesedioxide (EMD) showing better performance in alkaline cells. This is alsotrue of production of CMD by chemical processing. In particular,commercial producers of battery grade manganese dioxide may have beenreluctant to operate electrolysis or chemical processes at elevatedconditions of temperature and pressure, because of the concern of addedexpense. In contrast it is reported, for example, in commonly assignedapplication Ser. No. 09/788,754, filed Feb. 20, 2001 that operation ofelectrolysis for production of EMD at elevated temperatures betweenabout 115° C. and 155° C. and superatmospheric vapor-liquid equilibrium,or near equilibrium, can have some desirable processing advantages. Thiscan offset the added expense of production. For example, such elevatedconditions of temperature allows for the electrolysis to be carried outat significantly higher current density (based on total anode surface).As reported in this copending application, electrolysis for productionof EMD carried out at such elevated temperature, preferably between 115°C. and 155° C. and superatmopsheric pressure allows higher currentdensity of between 12.5 and 37 Amp/ft² (135 and 400 Amp/M²) morepreferably between 18 and 37 Amp/ft² (194 and 400 Amp/M²) based on anodesurface area, to be employed while avoiding passivation of the titaniumanode which typically occurs at very high current densities, e.g.greater than about 10 to 11 Amp/ft² (108 and 119 Amp/m²). Essentially,it has been determined that electrolysis at temperature between 115° C.and 155° C. eliminates the problem of passivation of a titanium anode.(Passivation occurs as an insulating oxide film builds up on the anode.)It has been discovered that when the electrolysis is conducted atelevated temperature above 115° C., e.g., between about 115° C. and 155°C. the problem of anode passivation of a titanium anode is essentiallyeliminated, even if the current densities are increased to a levelbetween 12.5 and 37 Amp/ft² (135 and 400 Amp/m²). Such benefit whencoupled with attainment of a better performing manganese dioxide undersuch operating conditions, could easily offset any added expenseincurred in such operation. Such better performing battery grademanganese dioxide is reported in the present application herein.

[0082] In any event because of the lack of activity or motivation,commercial producers have failed to recognize the interplay between BETsurface area and micropore area as reported by Applicant herein in orderto produce a superior battery grade manganese dioxide. The experimentalevidence herein presented suggests that a preferred manganese dioxidehaving a BET surface between 20 and 31 m²/g simultaneously with amicropore surface area of between 8 and 13 m²/g in the context of totalintraparticle porosity of between about 0.035 and 0.06 cm3/g, typicallybetween about 0.035 and 0.05 cm³/g. is obtainable. And it is morereadily obtainable if the manganese dioxide is made during electrolysisconditions carried out at the above referenced elevated temperatures andsuperatmospheric pressure conditions.

[0083] Although the graphs and descriptions of the preferredporosimetric coordinates are presented here in terms of intraparticleporosity measured by the BJH (Barrett, Joyner and Halenda) desorptionpore volume method, the micropore volume measured by the de Boer “t”method, the total surface area measured by the BET (Brunauer, Emmet,Teller) method and the micropore area measured by the de Boer “t”method, it will be appreciated by those skilled in the art andknowledgeable in porosimetry that many other possible experimental andtheoretical means of describing porosity and surface area are possible.Each method and theory leads to somewhat different numerical values, butin all cases, for a given material, an equivalent set of limits can beestablished. Thus, it would be possible to develop parallel sets ofvalues for intraparticle porosity, micropore volume, total surface areaand micropore area using the MP (Mikhail, Brunauer and Bodor) method,the DH (Dollimore and Heal) method, the DR (Dubinin and Radushkevich)method, the DA (Dubinin and Astakhov) method, the HK (Horvath andKawazoe) method or the SF (Saito-Foley) method.

[0084] There are also additional techniques for total surface area andmicropore surface area, such as the DFT (density functional theory)method.

[0085] All of the preceding methods and theories are based on gasadsorption experiments. Other methods of measuring porosity also exist.

[0086] Pore volume for the larger meso-macropores (only) can be measuredseparately by mercury intrusion.

[0087] Additionally, total intraparticle pore volume can be measured bycombining data from measurements of skeletal density (measured byvarious pycnometric methods such as helium, kerosene, or waterpycnometry) with measurements of the so-called envelop density (measuredby displacement of the unknown porous sample in a compressed solidmedium such as silica or graphite powder).

[0088] Thus many possible combinations are possible, each giving aparallel set of preferred values for BET area and micropore area as afunction of the total intraparticle porosity. No single set ofporosimetry theories is inherently better than another. We have foundthat the BET method, the de Boer “t” method and BJH desorption porevolume are adequate to the task of defining the preferred values ofthese 3 parameters, but any other combination of porosimetric theoriescould equally well be used. In each case the absolute numerical valuesfor the limits would be different but valid when measured by theappropriate method.

[0089] Accordingly, the invention is not intended to be limited to thespecific examples, but rather its scope is reflected by the claims andequivalents thereof.

What is claimed is:
 1. A particulate manganese dioxide having microporesand meso-macropores, said manganese dioxide having simultaneously a BETsurface area between about 20 and 31 m²/g, a micropore area betweenabout 8 and 13 m²/g and an average meso-macro pore radius greater than32 Angstom.
 2. The manganese dioxide of claim 1 wherein said manganesedioxide is in particulate form and said micropores and meso-macro poresare intraparticle pores and the total porosity of said manganesedioxide, based on pores within the manganese dioxide, is between 0.035cm³/g and 0.050 cm³/g.
 3. The manganese dioxide of claim 2 wherein themanganese particles have an average diameter between about 1 and 100micron.
 4. The manganese dioxide of claim 1 wherein said manganesedioxide is an electrolytic manganese dioxide.
 5. The manganese dioxideof claim 2 wherein the micropores are intraparticle pores having adiameter less than or equal to 20 Angstrom and the meso-macropores arepores having a diameter greater than 20 Angstrom.
 6. A particulateelectrolytic manganese dioxide product having micropores andmeso-macropores, said manganese dioxide having simultaneously a BETsurface area between about 20 and 28 m²/g and a micropore area between 8and 13 m²/g, and an average meso-macropore radius greater than about 32Angstrom, with the total porosity, based on pores within the manganesedioxide, being between about 0.035 cm³/g and 0.040 cm³/g.
 7. Themanganese dioxide of claim 6, wherein said manganese dioxide is inparticulate form and said micropores and meso-macro pores areintraparticle pores.
 8. The electrolytic manganese dioxide of claim 7wherein the manganese dioxide product is in particulate form having anaverage particle diameter between about 1 and 100 micron.
 9. Themanganese dioxide of claim 7 wherein the micropores are intraparticlepores having a diameter less than or equal to 20 Angstrom and themeso-macropores are pores having a diameter greater than 20 Angstrom.10. A particulate electrolytic manganese dioxide product havingmicropores and meso-macropores, said manganese dioxide havingsimultaneously a BET surface area between about 20 and 30 m²/g and amicropore area between 8 and 13 m²/g, and an average meso-macroporeradius greater than about 32 Angstrom, with the total porosity, based onpores within the manganese dioxide, being between about 0.040 cm³/g and0.045 cm³/g.
 11. The manganese dioxide of claim 10 wherein the manganesedioxide is in particulate form and said micropores and meso-macro poresare intraparticle pores.
 12. The electrolytic manganese dioxide of claim11 wherein the manganese dioxide is in particulate form having anaverage particle diameter between about 1 and 100 micron.
 13. Themanganese dioxide of claim 11 wherein the micropores are pores having adiameter less than or equal to 20 Angstrom and the meso-macropores arepores having a diameter greater than 20 Angstrom.
 14. A particulateelectrolytic manganese dioxide product having micropores andmeso-macropores, said manganese dioxide having simultaneously a BETsurface area between about 20 and 31 m²/g and a micropore area between 8and 13 m²/g, and an average meso-macropore radius greater than about 32Angstrom, with the total porosity, based on pores within the manganesedioxide, being between about 0.045 cm³/g and 0.050 cm³/g.
 15. Themanganese dioxide of claim 14 wherein the manganese dioxide is inparticulate form and said micropores and meso-macro pores areintraparticle pores.
 16. The electrolytic manganese dioxide of claim 15wherein the manganese dioxide is in particulate form having an averageparticle diameter between about 1 and 100 micron.
 17. The manganesedioxide of claim 15 wherein the micropores are pores having a diameterless than or equal to 20 Angstrom and the meso-macropores are poreshaving a diameter greater than 20 Angstrom.